1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device, in particular, a method for manufacturing a semiconductor device including a step of performing ion implantation.
2. Description of the Background Art
A step of performing ion implantation to form an impurity region is one of basic steps in a method for manufacturing a semiconductor device. The ion implantation may be performed for a plurality of times with different implantation energies in order to obtain a desired impurity concentration distribution in the impurity region in a depth direction. For example, Japanese Patent Laying-Open No. 2010-45363 discloses an example in which ion implantation is performed for five times in total in order to form, in silicon carbide, a doping distribution with a concentration of approximately 1×1017 cm−3 and a depth of approximately 0.6 μm. The implantation energies differ from one another among these five ion implantations. Specifically, the implantation energies are 40 keV, 100 keV, 200 keV, 280 keV, and 360 keV.
In the technique of the above-described publication, the plurality of ion implantation steps are performed with the different implantation energies. In consideration of facility cost, it is difficult to prepare one ion implanting device for each implantation energy. Hence, in the technique of the above-described publication, it is necessary to adjust a setting value for the implantation energy. However, when the implantation energy is changed, it takes a long time to stabilize the device. This leads to low efficiency in manufacturing semiconductor devices.